The third generation partnership project (3GPP) Release 6 defines MBMS, which is a counterpart of other multicast services operating in other communication standards, such as digital video broadcast-handheld (DVB-H). MBMS allows downlink data to be transmitted from a single source to multiple recipients in broadcast or multicast modes. The existing 3GPP release also defines the MBMS channels, scheduling, bearers, procedures, and the like.
In the 3GPP long term evolution (LTE) project, a new universal mobile telecommunication system (UMTS) evolved universal terrestrial radio access network (E-UTRAN) and evolved core network are introduced. This inevitably requires changes to the current specifications for MBMS so that the new architecture can support MBMS efficiently.
LTE requires the support of single cell and multi-cell MBMS transmissions. For multi-cell transmission, MBMS, (e.g., mobile TV), is transmitted on the coverage of a group of cells, MBMS may be transmitted on a multicast channel (MCH), soft combining of MBMS data at the receiver may be supported within a particular service group (i.e., single frequency network (SFN)), and synchronous transmission of MBMS data from multiple cells is possible.
To achieve synchronous data transmission in multiple cells in the LTE architecture, inter-cell scheduling is required. In Release 6, the synchronization is performed by a radio network controller (RNC). However, without an RNC in the new LTE architecture, alternative procedures have to be provided to facilitate multi-cell transmission.